Amorphous silicon

About: Amorphous silicon is a research topic. Over the lifetime, 26777 publications have been published within this topic receiving 423234 citations.

Thin film semiconductor deposition on free-standing ZnO columns

Abstract: We report the deposition of a-Si:H on thin films of free-standing single crystalline ZnO columns. The ZnO columns have a height of several μm and a diameter between 100 and 200 nm. The ZnO films are prepared in electrodeposition and have considerable potential for use in photoelectric thin film devices. Morphology, electronic parameters, and basic optical behavior, such as reflectance and light trapping efficiency, are reported. Amorphous silicon is deposited on the columns as a continuous smooth film with conformal coverage. Some possibilities of using these films in devices are discussed.

Optimization of hydrogenated amorphous silicon p–i–n solar cells with two-step i layers guided by real-time spectroscopic ellipsometry

Abstract: Hydrogenated amorphous silicon (a-Si:H) p–i–n solar cell performance has been optimized using a two-step i-layer growth process. This effort has been guided by real-time spectroscopic ellipsometry (RTSE) studies of the nucleation and growth of a-Si:H films by plasma-enhanced chemical vapor deposition at 200 °C using a variable H2-dilution gas flow ratio R=[H2]/[SiH4]. RTSE studies during film growth with R>15 reveal a transition from the amorphous to microcrystalline (a→μc) phase at a critical thickness that decreases with increasing R. From such results, the optimum two-step process was designed such that the initial stage of the i layer (∼200 A) is deposited at much higher R than the bulk to ensure that the film remains within the amorphous side of the a→μc phase boundary, yet as close as possible to this boundary at low i-layer thicknesses.

Mechanical and Electronic Properties of Thin-Film Transistors on Plastic, and Their Integration in Flexible Electronic Applications.

Abstract: The increasing interest in flexible electronics and flexible displays raises questions regarding the inherent mechanical properties of the electronic materials used. Here, the mechanical behavior of thin-film transistors used in active-matrix displays is considered. The change of electrical performance of thin-film semiconductor materials under mechanical stress is studied, including amorphous oxide semiconductors. This study comprises an experimental part, in which transistor structures are characterized under different mechanical loads, as well as a theoretical part, in which the changes in energy band structures in the presence of stress and strain are investigated. The performance of amorphous oxide semiconductors are compared to reported results on organic semiconductors and covalent semiconductors, i.e., amorphous silicon and polysilicon. In order to compare the semiconductor materials, it is required to include the influence of the other transistor layers on the strain profile. The bending limits are investigated, and shown to be due to failures in the gate dielectric and/or the contacts. Design rules are proposed to minimize strain in transistor stacks and in transistor arrays. Finally, an overview of the present and future applications of flexible thin-film transistors is given, and the suitability of the different material classes for those applications is assessed.

Sub–damage–threshold femtosecond laser ablation from crystalline Si: surface nanostructures and phase transformation

Abstract: Surface structures and structural transformations are investigated upon femtosecond laser ablation (800 nm, 120 fs) from crystalline silicon (100) targets placed under ultra-high vacuum. After repetitive illumination with several thousand laser pulses at intensities below the single shot damage threshold, at normal incidence, the crater morphology indicates the development of periodic structures at the crater bottom, with the orientation depending on the laser beam polarization. Periods of 200 nm and 600–700 nm, respectively, are shorter than the laser wavelength and appear as a result of surface instability. The ablation dynamics monitored by time-of-flight mass spectrometry shows the emission of positive silicon ions and clusters with kinetic energies of about 7 eV. Raman spectroscopy reveals phase transformations in the irradiated spot from Si-I to the polymorphs Si-III, Si-IV, Si-XII, and amorphous silicon as well as a stable, uncommon phase of hexagonal Si-wurzite.

Failure resistance of amorphous silicon transistors under extreme in-plane strain

Abstract: We have applied strain on thin-film transistors (TFTs) made of hydrogenated amorphous silicon on polyimide foil. In tension, the amorphous layers of the TFT fail by periodic cracks at a strain of ∼0.5%. In compression, the TFTs do not fail when strained by up to 2%, which is the highest value we can set controllably. The amorphous transistor materials can support such large strains because they lack a mechanism for dislocation motion. While the tensile driving force is sufficient to overcome the resistance to crack formation, the compressive failure mechanism of delamination is not activated because of the large delamination length required between transistor layers and polymer substrate.